DESCRIPTION: Substance users are at substantially increased risk for HIV and HCV infection, as well as for HIV/HCV co- infection. Yet fewer than half of U.S. substance abuse treatment programs offer HIV testing to their clients on- site or through referral to outside agencies, and only about one third offer HCV testing. In contrast, most syringe exchange programs (SEPs) conduct on-site HIV and HCV testing. During the current funding period, we showed the clinical and economic value of on-site rapid HIV and HCV testing in substance abuse treatment programs, even where there is a low prevalence of undiagnosed HIV. On a practical level, however, lack of reimbursement for HIV and HCV testing has been a barrier to implementation in substance abuse treatment programs. Under the Affordable Care Act (ACA), HIV and HCV tests are now required to be reimbursed by health insurers without any copayment requirement. Results from a currently-funded nationally representative survey exploring the ACA's influence on substance abuse treatment program practices will provide a platform for a further in-depth study of testing reimbursement and budget impact. During the current funding period, we also conducted model-based analyses of the cost-effectiveness of hypothetical HCV linkage to care initiatives. We concluded that additional investments that address the limited linkage and care coordination infrastructure for HCV compared to HIV would be cost-effective. New effectiveness and cost data are now available from a recently completed randomized trial of HCV care coordination in substance abuse treatment programs. These data will allow us to estimate the cost-effectiveness of specific linkage and care coordination initiatives and their impact on program budgets. The economic value and budget impact of testing and linkage activities being conducted in syringe exchange programs has not been evaluated, and research is needed to collect data and conduct exploratory modeling studies. Our specific aims in the next funding period include: 1) determining the budget impact on substance abuse treatment programs of on-site HIV and HCV testing in the context of ACA and other reimbursement and organizational factors, 2) assessing the cost-effectiveness and budget impact of adding HCV care linkage and coordination services in substance abuse treatment programs, and 3) exploring the budget impact and cost-effectiveness of providing similar testing and care linkage services in SEPs. These aims innovatively leverage NIH research investments in substance abuse treatment program surveys, a clinical trial of HCV care coordination, and a computer simulation model of HCV and HIV disease. The approach is innovative in that applies mixed methods to evaluating budget impact, extends clinical HCV care coordination trial results using a computer simulation model to project cost-effectiveness, and is the first study to explore the economic value and budget impact of HIV and HCV testing in SEPs. The results of this study will assist policy makers and program managers in addressing cost barriers and taking advantage of reimbursement opportunities to provide much needed HIV and HCV testing and care linkage services to their clients.